1. Field of the Invention
The present invention relates to an image blur suppression device of a camera for suppressing image blur due to shaking of the photographer's hands during photography. More particularly, the present invention relates to the alignment of an image blur suppression lens and the alignment of an electromagnetic actuator of an image blur suppression device, based on the sag of supporting members.
2. Description of the Related Art
Image blur suppression devices suppress, or reduce, blurring of an image projected onto an image plane by an optical system. Motion is typically imparted to the optical system by vibrations affecting the optical system or in a surrounding holding member. In general, conventional image blur suppression devices cause an image blur suppression lens to shift counter to the motion of the optical system so as to shift the image projected by the optical system relative to the optical system.
Blurring of an image on film (called "image blur") is an undesirable consequence of vibrations affecting a camera. Such vibrations are typically caused by the shaking of the photographer's hands during exposure of the film. Conventional cameras suppress image blur by moving an image blur suppression lens in a direction which is perpendicular to the optical axis, thereby compensating for detecting vibrations. For example, Japanese Patent Publication Kokai 2-66536 discloses a camera in which an image blur suppression lens is supported by elastic support rods and, while supported, is moved in a direction perpendicular to the optical axis by an electromagnetic actuator.
An electromagnetic actuator generally includes a magnet and a coil. The magnet is fixed to a base and the coil is connected to the image blur suppression lens. An electromagnetic force is generated when an electric current is supplied to the coil, thereby moving the image blur suppression lens.
The use of the elastic support rods makes it unnecessary to rely on complicated and expensive slide and drive mechanisms to move the image blur suppression lens. Also, the use of elastic support rods makes the camera lighter and more compact.
However, a camera having elastic support rods experiences problems due to the force of gravity acting on the support rods. For example, the most common photographic posture is for the photographer to hold the camera so that the optical axis of the photographic optical system is approximately parallel to the earth's surface. During this positioning, the elastic support rods sag due to the weight of the support rods and the weight of the image blur suppression lens. As a result, the optical center of the image blur suppression lens becomes undesireably offset from the optical axis of the photographic optical system. This offset also causes an undesirable offset between the magnet and the coil of the electromagnetic actuator.
Further, the process of exposing film inside the camera to light from a photographic subject requires the steps of (a) compensating for the offset of the image blur suppression lens by performing a centering process to align the optical axis of the image blur suppression lens with the optical axis of the photographic optical system and, after the centering process is complete, (b) moving the image blur suppression lens to compensate for detected vibration. Therefore, as a result of a large offset, the centering process requires a large amount of time and consumes a large amount of electricity. Also, a large amount of time for centering causes the start of exposure to be delayed.